This invention relates to a centrifuge rotor, and in particular, to a swinging bucket centrifuge rotor having a windshield a portion which is movable with respect to the rotor shaft from a rest to a closed position.
In the design of nonevacuated centrifuge rotors tradeoffs are made between the volume of material able to be carried by the rotor and the relative centrifugal force able to be generated by rotation of the rotor. In centrifuge rotors of the swinging bucket type the volume of material able to carried by the rotor is functionally related to the number of swinging buckets able to be disposed on and carried by the rotor as well as the volume of each of the buckets.
The relative centrifugal force developed by a rotor is windage limited. That is, for a given rotor volume the maximum operating speed at which that rotor may rotate is usually limited by the drive torque available to the rotor at that speed. Thus increasing rotor volume, as by increasing the number or size of the buckets, may have an adverse effect upon the amount of relative centrifugal force able to be generated by the rotor.
In the case of a swinging bucket rotor losses are engendered by the pumping action of the rotor's arms as the rotor is rotated. The pumping losses are minimized by providing a windshield which completely encloses the rotor. Conventional windshields include a lower portion which is fixed to the rotor shaft and an upper cover which is removable from the shaft. With the cover removed material to be centrifuged is introduced into the buckets and the cover replaced. Driving torque is then applied to the rotor causing the buckets to swing from their rest position (in which the axis of each bucket lies parallel to the rotor's axis of rotation) to their operating position (in which the axis of each bucket extends substantially perpendicularly to the axis of rotation). It should be noted that in the conventional windshielded rotor the windshield encloses the buckets while they occupy all altitudes from the rest to the operating position.
Although windshielding a swinging bucket rotors minimizes pumping losses and thereby contributes to increased relative centrifugal force it is not possible to merely increase the volume of the buckets within the windshielded rotor and thereby increase rotor volume while maintaining the same relative centrifugal force. This is because the configuration of the windshield itself imposes windage losses on the system which are increased as the windshield increases in size.
Accordingly, it is believed desirable to provide a swinging bucket centrifuge rotor wherein the relative centrifugal force available for a given rotor volume is increased.